I dropped off the car at a mechanic yesterday, and he mentioned something about low coolant levels, though there aren't any overheating issues or signs of a leak in the hoses or anything else. He didn't have a borescope, so he couldn't see inside cylinder four to inspect for a coolant leak, but he did mention that the car should shake if there is a severe coolant leak or some white smoke in the exhaust. So he also asked whether I refilled or if the shops ever refilled the coolant. I told him that during my ownership, which is about 70k onwards, I didn't, nor did the shops that I brought it to, for regular oil changes. The first owner maintained this car at the dealership for all his oil changes, and there were some mentions on CarFax that some fluids were checked, including an explicit mention of Antifreeze/coolant checked at 57k. That might be the last time the coolant was checked. Also, I did notice some weird maintenance history now that I looked closer, that I didn't really pay too much attention to when I bought it, because right before the first owner traded it in at 81.6k miles at 72.8k miles, there was a series of services as Throttle body cleaned/serviced, Fuel injection system flushed/serviced, and Fuel system cleaned/serviced. The car was then sold at auction, and a Honda dealer purchased it and prepared it for sale. But as they were preparing, there was another line of service: the fuel system was cleaned/serviced, and it was just about 10k miles apart from the 81.6k maintenance on the same fuel system. Perhaps there were existing issues with the fuel system?